Device to dampen fluctuations in the concentration of a substance in a flowing stream of fluid

ABSTRACT

A process for smoothing out or damping concentration fluctuations of a substance in a fluid stream comprising dividing the stream into a number of substreams, feeding each of the substreams to a common point while introducing different time delays of arrival of each substream at the common point and then recombining the substreams into the single larger stream again. An apparatus for performing the above process comprising a combination of means capable of dividing the influent stream into a number of substreams, means capable of imparting different time delays to each substream for arrival at some common point and means for recombining the substreams.

ilnited States Patent [191 Troy 1 Dec. 31, 1974 DEVICE TO DAMPENFLUCTUATIONS IN THE CONCENTRATION OF A SUBSTANCE IN A FLOWING STREAM OFFLUID [75] Inventor: Joseph C. Troy, Pittsburgh, Pa. [73] Assignee: NUSCorporation, Rockville, Md. [22] Filed: June 21, 1973 [21] Appl. No.:372,366

Harder 259/4 3,462,130 8/1969 Holthausen 259/18 Primary Examiner-RobertW. Jenkins Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, Zinn &Macpeak [5 7] ABSTRACT A process for smoothing out or dampingconcentration fluctuations of a substance in a fluid stream comprisingdividing the stream into a number of substreams, feeding each ofthesubstreams to a common point while introducing different time delaysof arrival of each substream at the common point and'then recombiningthe substreams into the single larger stream again. An apparatus forperforming the above process comprising a combination of means capableof dividing the influent stream into a number of substreams, meanscapable of imparting different time delays to each substream for arrivalat some common point and means for recombining the substreams.

4 Claims, 8 Drawing Figures PAIENTEU I 1974 3,857, 551

A INLET FIG. 7

DEVICE TO DAMPEN FLUCTUATIONS IN THE CONCENTRATION OF A SUBSTANCE IN AFLOWING STREAM OF FLUID BACKGROUND OF THE INVENTION 1. Field of theInvention The present invention relates to a device, termed anequalization basin or equalization tank, designed to smooth out ordampen fluctuations in concentration of a substance in a fluid system.In addition, the present invention also relates to a process foraccomplishing the same result.

2. Description of the Prior Art Obviously, in fluid systems where aconstant concentration of a substance in a fluid is desired ornecessary, fluctuations in the concentration of the substance in thefluid are undesirable or even potentially harmful. As an example, if thesalt concentration in a liquid varied with time from I to 3 pounds pergallon with a mean value of 2 pounds per gallon over a long period oftime, the perfect equalization device would accept this varyingconcentration as an input, and deliver liquid at a constant effluentconcentration of 2 pounds per gallon. Such a perfect equalization deviceis not possible since it would have to be of infinite size. The bestknown and easiest to calculate practical equalization device for fluidsystems is a complete mix basin. This device consists of a pond or tankwith a large, powerful mixer in it.

The term complete mix" implies that the contents of the tankor pond areuniform at every point and equal to the effluent concentration. Theinfluent enters through a pipe at one side and is instantly mixed withthe entire contents of the tank or pond. It can be shown mathematicallythat the rate of change of concentration of the effluent with respect totime is slower than the rate of change of the influent concentrationwith respect to time, and that the magnitude of the change in theconcentration of the effluent is proportionately less than the magnitudeof the change of concentration of the influent by the amount that therate of change of effluent concentration is slower than the rate ofchange of influent concentration. The ratio of the two rates of changeand the two magnitudes of change is a function of the holding time ofthe complete mix equalization device.

US. Pat. No. 3,404,869 (Harder) discloses an interfacial surfacegenerator, i.e., a mixing device, or static mixer which consists of anumber of chambers having two or more inlets and two or more outlets,the inlets and outlets being noncoplanar and the planes intersecting anaxis of flow. The device mixes the incoming fluid in such. a manner thateach of the outlet conduits contains a portion of the material from eachof the inlet conduits.

Other known mixing devices are disclosed in the following U.S. Pat.Nos.: 3,291,456; 3,306,587, and 3,547,410.

The primary difficulty of the prior art devices and processes is thattheir efficiency is unacceptable while some, in addition, requirecomplex apparatus and high energy inputs to achieve good results.

It is-therefore a primary object of the present invention to provide asimple and efficient process for damping fluctuations in concentrationof a substance in a fluid without the above disadvantages.

2 It is a further object of the present invention to provide a simpledevice by which such a process can be performed.

Other objects, features and advantages will become apparent from theensuing description.

SUMMARY OF THE INVENTION The process of the invention comprises:

1. dividing a stream of fluid containing a substance (whoseconcentration fluctuations in the fluid one wishes to dampen) into anumber of substreams;

2. feeding each of the resulting substreams to a common point andintroducing time delays of arrival of each substream at the point witheach time delay of arrival being different for each substream; and

3. recombining the substreams into the single larger stream again.

The present invention also relates to an apparatus for performing theabove process. Generally, the apparatus comprises a combination of meanscapable of dividing the influent stream into a number of substreams,means capable of imparting different time delays to each substream forarrival at some common point and means for recombining the substreams.Specific processes and apparatus will be discussed hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 represent simple deviceswhich explain.

the theory of the present invention.

FIGS. 3 through 7 show possible shapes of devices which may be employedin the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS The present invention is applicableto any fluid (gas and liquid) stream containing a foreign substancewhose concentration gradient may vary with time or,

riod and then back to blue again, gives the following results. Assumethat the main stream is divided into five substreams in the equalizationdevice and that the time delay of arrival at the designated common pointof the first substream is zero, of the second substream 2 minutes, ofthe third substream is 4 minutes, of the fourth is 6 minutes, and of thefifth is 8 minutes.

When the red slug comes along, the first substream will start to run redat once and will run red for 2 minutes (the length of the red pulse),but the other four streams will still be running blue because of thetime delay. Since only one of five streams is red, the concentration ofred in the effluent from the device will be only 20 percent of theconcentration in the input stream.

At the end of the first two minutes, the first substream will start toflow blue again,but the second one (two minute time delay) will start toflow red. Substreams 3, 4 and S will still be'blue because of theirlonger time delays so the concentration of red in the effluent willcontinue at 20 percent of the influent pulse value.

It can be seen that this situation will repeat itself across all fivesubstreams. In this case, the device has taken an input pulse of 2minutes duration and spread it out as an output pulse of only 20 percentof the initial concentration, but 5 times as long in duration.

The above example is simplistic in nature for purposes of illustrationonly. In actuality, the influent stream need not be divided into adiscrete number of individual substreams and treated separately andfinally recombined. Rather, the influent stream enters the device as asingle stream, but the geometry of the device in effect divides theinfluent stream into what can be considered as a very large number ofsubstreams with the difference in time delay of arrival at the commonpoint becoming extremely small. To illustrate the point, refer to FIG.1, which schematically shows a simple form of a device whichaccomplishes the desired results of the present invention. The flow offluid through the device is indicated by the arrows. The fluid entersthe device via pipe 1 and then flows into a manifold 2, from which it isdivided into three separate streams designated 3, 4, and 5 in theFigure. These three streams are again recombined in exit manifold 6 andthe fluid leaves the device via exit pipe 7. Assuming the concentrationof a substance in the fluid stream reaches a peak value x periodically,the fluid stream exiting from the device as shown in FIG. 1 would have aconcentration equal to some percentage ofx depending on the ratio of theduration of the peak concentration value to the average of the delaytime of the substreams. The lower this ratio is, the better theequalization.

The above theory forms the basis of the present invention, and asuitable apparatus for the practice of the present invention isschematically illustrated in FIG. 2. Inlet pipe 8, inlet manifold 9,exit manifold 11 and exit pipe 12 correspond respectively to the relatedmeans in FIG. 1. However, the three pipes (3, 4 and 5) of FIG. 1 havebeen replaced by a continuous flat tray in FIG. 2. The fluid flows intothe tray over a weir provided inlet manifold 9, which runs the width ofthe tray, and similarly, the fluid flows from the tray into exitmanifold 11 over a similar weir in the latter. In effect,

the device shown in FIG. 2 has divided the inlet streaminto an infinitenumber of substreams, although the inlet stream is not actually dividedinto discrete substreams. Depending upon the width of the tray and thelength and depth of the same, any desired degree of equalization can beobtained, and one skilled in the art can easily see how the device ofthe present invention functions to equalize or dampen fluctuations inconcentration of a substance in the fluid flowing through the device.

In the present invention, equalization essentially equal to a completemix basin of the prior art and the same size, is accomplished with nopower input at all. It is simply the geometry of the device which makesit work.

The basin or tank can be made essentially into any size and shape, thesize depending of course upon the volume of fluid flowing through thedevice, the degree of equalization or dampening desired, etc., and theshape of the device of course being such as to assure the delay times inthe theoretical substreams necessary to achieve equalization.

FIG. 3 illustrates a typical tank or pond which can be employed toaccomplish the purpose of the present invention. The flow of fluidthrough the device is indicated by the arrows in the Figure. The fluidenters the device along the hypotenuse of the triangle and flowsoutwardly therefrom toward one of the sides, where it is collected bysuitable means and withdrawn from the device along that side. Theparticular configurations of the inlet and outlet manifolds is notcritical. They may comprise a trough-like apparatus, wherein the fluidflows over the weir formed by the lower side of the trough(schematically illustrated in cross-section in FIG. 4). The edge overwhich the fluid flows may either be flat or may be rippled in order toachieve the effect which is more nearly alike a large number of smallseparate streams flowing over the edge of the inlet and exit manifolds.In addition, a plurality of pipes may be provided along the inletmanifold, each pipe being capable of discharging an equal volume ofwater into the tank.

Generally, any means which distributes the fluid uni-' 5b) to twoadjacent sides of the pond or tank where it is collected-by suitablemeans (e.g., the troughs shown in sections BB and C-C in FIG. 5b).

Another alternative embodiment of the present invention is shown inFIGS. 6 and 7, FIG. 6 being a plan view and FIG. 7 being a crosssectionalong the line A-A of FIG. 6. The inlet may simply be a pipe which feedsthe fluid to the tank at a point off-center thereof. The outlet shown inFIGS. 6 and 7 (a circular flat, level weir) surrounds the entirecircumference of the tank as shown.

Generally, any shape, tank or pond (dug into the ground) is suitable forthe present invention as long as the geometry of the device is such asto provide a series of delay times for travel of the fluid between theinlet and the outlet.

The only criteria for the design of the inlets and outlets is that thevolume of water contained therein must be small relative to the volumecontained in the tank or pond between them, that the flow of water bedischarged (or collected, as the case may be) uniformly over the lengthof the inlet or outlet devices and that the number of discharge orcollection points from or to the inlet or outlet devices to the pond ortank be large. This can generally be accomplished by providingrelatively small inlet and outlet troughs of the type shown in FIG. 4,where the water flows uniformly over the lowermost edge thereof andwherein the number of discharge and collection points can be consideredinfinite.

The effectiveness of the equalization depends most importantly upon thevolume of fluid which is contained in the pond or tank between the inletand outlet, since the larger the volume, the longer the averageretention time of the fluid in the pond or tank, of course, a longerretention time favoring a greater equalization or dampening of thefluctuations of the variable concentration which occurs in the inletstream.

One skilled in the art can apply the techniques described above to anysystem where it is desirable or necessary to eliminate greatfluctuations in concentrations of a substance in a fluid stream, orsimilarly, to eliminate great fluctuations in temperature of a fluidstream, etc. For example, the present invention finds utility in theregeneration of zeolite softeners. Such softeners are normallyregenerated with strong salt so lutions, and usually on a batch basisresulting in periods of time where no waste salt solution is beingdischarged, and other times when it is being discharged at a high flowrate. Without equalizing the stream of waste salt leaving the plant, attimes the concentration of salt in the plant effluent may be so high asto be potentially harmful. However, if the plant effluent is equalizedusing the present invention, the concentration of salt in the effluentwould be essentially the average concentration over a long period oftime which would of course be much lower than the peak values whichwould occur without equalization. As a result, the continuous lowerconcentration of salt would be much less harmful to the environment.

The present invention also finds utility in a process for treatingliquid waste from a metallic plating plant. Normally, the metallicelement is removed from the waste stream prior to discharging the streamto waste. If, however, at several times during the daily operation ofthe plant, large concentrations of concentrated metallic platingsolutions are fed to the waste disposal operation, the entire systemmust be capable of removing this large concentration of the metallicelement from the waste stream prior to discharging it. However, forthose periods in the daily operation where a much lower concentration ofmetallic waste is fed to the waste treatment operation, the metallicremoval system is greatly over-sized. By installing an equalizationdevice according to the present invention in the waste treatmentoperation ahead of the metallic element removal system, theconcentration of the metallic elements in the waste stream is reduced toan essentially continuous concentration which is substantially below thepeak concentration normally encountered. The result of course is aconsiderable cost savings in the metallic element removing means, sinceit need only be designed to handle the equalized concentration insteadof the peak concentration.

Another example, and very pertinent to the present invention, is in thedesign of a biological oxidation system to remove dissolved organiccompounds from a flowing stream of water. Normally, a bio-oxidationsystem must be designed extremely accurately, since they system performspoorly if it is overloaded and equally poorly if it is underloaded.Thus, if there is any significant concentration variation at all of theorganic in the stream which is the input to the biological oxidationsystem, it is essential to equalize the concentration of the organic inthe water, and therefore the present invention finds particular utilityin such an operation.

Although the present invention has been described above with referenceto preferred embodiments, it is to be understood that variations may bemade therefrom without departing from the spirit and scope of theinvention, as is apparent to those skilled in the art.

What is claimed is:

1. An apparatus for damping variable concentrations of a substance in aliquid stream, said apparatus comprising:

a triangular-shaped liquid container, means for feeding said liquidstream into said liquid container including a first, inlet manifoldlocated along the hypotenuse of said triangle,

means including said first inlet: manifold for dividing said stream intoa plurality of substreams, and

mean for collecting said substreams at a common point comprising asecond, liquid outlet manifold located along one of the opposite sidesof said triangle;

whereby, said substreams dividing at said first inlet manifold and beingcollected by said outlet manifold at said hypotenuse and said sideopposite thereto, respectively, imparts time delays to each substreamfor arrival at said common point to provide a single liquid stream whichhas a substantially constant concentration of said substreams which issubstantially lower than the peak or highest concentration of saidsubstreams in said stream prior to treatmentwith said apparatus.

2. An apparatus as claimed in claim 1, wherein said triangular shapedcontainer comprises a basin, wherein said first, inlet manifoldcomprises a first trough along the hypotenuse of the triangular shapedbasin, and said second, outlet manifold comprises a second troughlocated along one of the opposite sides of said triangular shaped basin;whereby, said basin imparts'time delay to said liquid stream whichdivides into a pluralityof substreams and moving from one trough to theother with said trough located along said opposite side acting torecombine said substreams at a common point to provide a single streamwhich has a substantially constant concentration of said substance whichis substantially lower than the peak or highest concentration of saidsubstance in said stream prior to treatment with said apparatus.

3. An apparatus for damping variable concentrations of a substance in aliquid stream, said apparatus comprising:

means capable of dividing said stream into a plurality of substreams;means for feeding each of said substreams to a common point; means forimparting time delays to each substream for arrivalat said common point;and

means for recombining said substreams at said common point to provide asingle stream which has a substantially constant concentration of saidsubstance which is substantially lower than the peak or highestconcentration of that substance in said stream prior to treatment withsaid apparatus, said apparatus being rectangular in form and including atrough disposed along the, diagonalof said rectangle, with said fluidflowing over both sides of said trough and toward the two sides of saidrectangle opposite said diagonal, and wherein means for collecting saidsubstreams at said common point comprises troughs disposed along saidtwo opposite sides and meeting at their intersection. 4. An apparatusfor damping variable concentrations of a substance in a liquid stream,said apparatus comprising:

7 8 means capable of dividing said stream into a plurality and wherein,said apparatus is in the form of a circuof substreams; v lar tank andsaid means capable of dividing said liqmeans for feeding each of saidsubstreams to a comuid stream into a plurality of substreams comprisesmon point; an inlet pipe for feeding said liquid stream into said meanscapable of imparting time delays to each subcircular tank at a pointoff-center thereof, and said stream for arrival at said common point;and means for collecting said plurality of substreams at means forrecombining said substreams at said comsaid common point comprises atrough surrounding mon point to provide a single stream which has a thecircumference of said circular tank on the insubstantially constantconcentration of said subside thereof such that the fluid flows fromsaid inlet stance which is substantially lower than the peak or 10 pipeoutwardly toward the circumference of the highest concentration of saidsubstance in said circular tank and is collected within said trough.stream prior to treatment with said apparatus;

1. An apparatus for damping variable concentrations of a substance in aliquid stream, said apparatus comprising: a triangular-shaped liquidcontainer, means for feeding said liquid stream into said liquidcontainer including a first, inlet manifold located along the hypotenuseof said triangle, means including said first inlet manifold for dividingsaid stream into a plurality of substreams, and mean for collecting saidsubstreams at a common point comprising a second, liquid outlet manifoldlocated along one of the opposite sides of said triangle; whereby, saidsubstreams dividing at said first inlet manifold and being collected bysaid outlet manifold at said hypotenuse and said side opposite thereto,respectively, imparts time delays to each substream for arrival at saidcommon point to provide a single liquid stream which has a substantiallyconstant concentration of said substreams which is substantially lowerthan the peak or highest concentration of said substreams in said streamprior to treatment with said apparatus.
 2. An apparatus as claimed inclaim 1, wherein said triangular shaped container comprises a basin,wherein said first, inlet manifold comprises a first trough along thehypotenuse of the triangular shaped basin, and said second, outletmanifold comprises a second trough located along one of the oppositesides of said triangular shaped basin; whereby, said basin imparts timedelay to said liquid stream which divides into a plurality of substreamsand moving from one trough to the other with said trough located alongsaid opposite side acting to recombine said substreams at a common pointto provide a single stream which has a substantially constantconcentration of said substance which is substantially lower than thepeak or highest concentration of said substance in said stream prior totreatment with saId apparatus.
 3. An apparatus for damping variableconcentrations of a substance in a liquid stream, said apparatuscomprising: means capable of dividing said stream into a plurality ofsubstreams; means for feeding each of said substreams to a common point;means for imparting time delays to each substream for arrival at saidcommon point; and means for recombining said substreams at said commonpoint to provide a single stream which has a substantially constantconcentration of said substance which is substantially lower than thepeak or highest concentration of that substance in said stream prior totreatment with said apparatus, said apparatus being rectangular in formand including a trough disposed along the diagonal of said rectangle,with said fluid flowing over both sides of said trough and toward thetwo sides of said rectangle opposite said diagonal, and wherein meansfor collecting said substreams at said common point comprises troughsdisposed along said two opposite sides and meeting at theirintersection.
 4. An apparatus for damping variable concentrations of asubstance in a liquid stream, said apparatus comprising: means capableof dividing said stream into a plurality of substreams; means forfeeding each of said substreams to a common point; means capable ofimparting time delays to each substream for arrival at said commonpoint; and means for recombining said substreams at said common point toprovide a single stream which has a substantially constant concentrationof said substance which is substantially lower than the peak or highestconcentration of said substance in said stream prior to treatment withsaid apparatus; and wherein, said apparatus is in the form of a circulartank and said means capable of dividing said liquid stream into aplurality of substreams comprises an inlet pipe for feeding said liquidstream into said circular tank at a point off-center thereof, and saidmeans for collecting said plurality of substreams at said common pointcomprises a trough surrounding the circumference of said circular tankon the inside thereof such that the fluid flows from said inlet pipeoutwardly toward the circumference of the circular tank and is collectedwithin said trough.